Controlling the material properties and biological activity of lipase within sol-gel derived bioglasses via organosilane and polymer doping

The development of optical biosensors based on sol-gel entrapped proteins r equires a detailed understanding of the evolution of the physicochemical pr operties of the material, their affects on protein function, and how these factors can be tailored by processing conditions. In this study, the polyme r additives poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG) were dispersed into sol-gel processed materials derived from tetraethyl orthosil icate (TEOS) alone or copolymerized with methyltriethoxysilane (MTES) or di methyl-dimethoxysilane (DMDMS), and their effects on the chemical and physi cal properties of the materials were monitored. In general, the physical pr operties, including transmittance and resistance to cracking, improved with increasing PEG concentration, but deteriorated with PVA content. The spect roscopic data obtained from entrapped 7-azaindole and 6-propionyl2-(dimethy lamino)naphthalene suggested that the inclusion of polymers and organic moi eties into the matrix affected both the homogeneity of the materials and th e polarity of the internal environment, with PEG reducing and PVA increasin g the internal polarity. In light of these results, preliminary studies wer e performed on the effects of organic and polymer content on the initial an d long-term activity of entrapped lipase. Concomitant with the material dat a, PVA tended to have a detrimental affect on lipase activity, while PEG pr ovided a concentration-dependent enhancement of the enzyme activity. This s tudy demonstrates for the first time that durable, optically transparent ma terials with significant lipase activity can be prepared and that optimal m aterials are produced with TEOS as a precursor and a few weight percent of low molecular weight PEG as an additive, with no need for organosilane prec ursors.